Astronomers have identified a previously unknown source of cosmic γ-radiation.

High-energy γ-rays are released in extremely energetic events such as pulsars and supernovae. But they were thought to be unlikely products of classical novae: explosions that occur on the surfaces of compact, burnt-out stars called white dwarfs as they collect material from their neighbours in the binary system. The only nova previously seen emitting such rays came from an unusual type of star system. Now Teddy Cheung at the Naval Research Laboratory in Washington DC and his colleagues have used NASA's Fermi Telescope to detect high-energy γ-rays coming from three classical novae.

The otherwise unremarkable properties of the three stars suggest that such emissions could be common. It is not yet clear how particles surrounding the stars might be accelerated enough to produce the energetic radiation.

Science 345, 554–558 (2014)